Hi I don't know if screen-share/co-browse support for Chat v2 (widget v2) is in the roadmap however as a workaround I could think of, while in the chat interaction with the customer, making an outbound call on behalf of a queue to that customer (of course it would be necessary to ask her/his phone number) that way it's possible to start a screen-share/co-browse session for that voice call.
However, I wonder if it's possible, one way or another, to associate/link that voice conversation with the original chat conversation.
There is no API endpoint/request to link/associate the voice conversation with the original chat conversation.
But it depends how and where you are planning to leverage this piece of information (the fact that the chat is tied to the voice conversation).
If your customer has an External Contact configured, and if you make an Analytics query for Conversation details (filtering on the External Contact ID), you could check (parsing/via code) if some chat conversations occurred simultaneously with a voice conversation.
Or if it just about keeping a trace of the fact that the chat was associated with the voice call, you could do a client side integration, probably using the Interaction Widget integration one, and have your custom client code attach some key/value pairs in the chat conversation or the voice conversation as participant data/attributes. But this requires coding and implementing this client side code that leverages Platform API.